000 AXPZ20 KNHC 301451 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1425 UTC Sat Dec 30 2017 Tropical Weather Discussion for the eastern Pacific Ocean from the Equator to 32N, east of 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis. Based on 1200 UTC surface analysis and satellite imagery through 1500 UTC. ..SPECIAL FEATURES... Gale Warning: A cold front is crossing 140W north of 22N currently, associated with a deep layer low pressure system northwest of the area that has been moving slowly northward over the past couple of days. The front will weaken today as it moves farther east and will dissipate tonight, ahead of a second stronger front entering the region. Strong to minimal gale force winds will follow the second front Sun night into Mon as high pressure builds behind the front along with a push of cooler air. Gale will be limited to the waters north of 28N between 135W and 140W, and will diminish below gale force through late Mon as the low pressure moves farther east and weakens and the cold front modifies as it continues eastward. Very rough to high seas can be expected in the area of gales building as high as 20 ft late Sun and early Mon. This will be due in part to the gales but also likely in part to NW swell entering the area. The large seas will subside to 8 to 10 ft through mid week. Refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 08N82W to 06N100W, where it transitions to the intertropical convergence zone and continues west to 09N140W. Scattered moderate convection is noted from 07N to 10N between 100W and 110W, and from 10N to 12N between 110W and 115W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... In the Gulf of Tehuantepec, winds have finally diminished below gale force as high pressure north of the area weakens, and winds veer more easterly. Strong gap winds will pulse again tonight due to overnight drainage flow, with seas briefly reaching 8 ft. A strong cold front will push into the Gulf of Mexico late Sunday, reaching the Bay of Campeche Monday, with strong high pressure in its wake expected to induce the next gale force gap wind event over the Gulf of Tehuantepec. This next gale force gap winds event has the potential to be a strong and long lasting event, persisting for much of the next week. Elsewhere, tranquil marine conditions are expected with light to gentle winds prevailing over the forecast waters. Seas in the range of 3 to 5 ft will continue over the offshore waters, while seas in the 1 to 3 ft range will prevail in the Gulf of California. A sharp upper trough is supporting widespread cloudiness and maybe a few showers across Baja California Sur and adjacent waters. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... NE winds will pulse to fresh to strong over the Gulf of Papagayo through the middle of next week. Light to gentle NE to E winds will prevail elsewhere N of 09N, with gentle to moderate S to SW winds expected S of 09N. REMAINDER OF THE AREA... Please see above in special features section for more on the gale warning over the northwest waters, and associated swell. A pair of surface troughs persist from roughly 10N to 15N between 120W and 130W. Earlier scatterometer passes indicate winds of 20 to 25 kt between the troughs and 1022 mb high pressure centered north of the area. Concurrent altimeter satellite passes indicate seas to 8 ft in the areas of strong winds. A surface trough will persist and shift northward through Tue ahead of advancing front, supported by a broad mid to upper trough slowly moving into the area from the west and persisting over the region west of 130W through at least mid week. Strong winds and seas to 8 ft are expected with the associated surface trough by Tue as it moves northward along 125W from 20N to 25N. Long period northwest swell in excess of 8 ft will cover most of the area north of 10N and west of 125W through mid week. $$ Christensen